1. The Field of the Invention
The present invention generally relates to high speed optoelectronic modules and host devices. In particular, some example embodiments relate to a mechanical platform for pluggable modules and host devices
2. The Related Technology
Conventional mechanical platforms implemented in optical networks include a pluggable module configured to be plugged into a host device to convert electrical data signals to optical data signals and vice versa. Specific functionality, dimensions, and/or other functionality of such mechanical platforms are often standardized by a multi-source agreement (“MSA”), such as the X2 MSA, XPAK MSA, and/or XENPAK MSA, for example.
Traditional pluggable modules, including X2, XPAK, and XENPAK form-factor modules, include a narrow channel defined along opposite sides of the module that run the length of the module. Host devices include corresponding narrow guiderails. To plug such a module into a host device, the module channels are aligned with the host guiderails and the module is pushed into the host device, the module channels engaging the host guiderails to ensure proper alignment of the module within the host device. Once plugged in, a module connector in the back of the module and a host connector in the host device provide an electrical interface between the module and the host device.
Additionally, traditional pluggable modules are commonly secured in host devices by two short thumbscrews which engage threaded receptacles in the front panel of the host device. To this end, the module typically includes an oversize module front panel with two flanges that extend outward from opposing sides of the module, one thumbscrew being inserted through each flange. The flanges typically overlap a significant amount of the host front panel to provide enough metal for the thumbscrews to thread into. The overlap is increased by the requirement that the thumbscrews avoid the space behind the module front panel and the host front panel occupied by the module itself and the narrow guiderails of the host device.
As a result of the required overlap, the footprint of the module front panel and flanges extends significantly beyond the footprint of the main body of the module as viewed from the front of the module. Consequently, the maximum number of modules that can be plugged into a single host device is limited by the module front panel and flanges, and not by the main body of the module.
Further, the attachment of traditional pluggable modules to the front panel of the host device can make containment of electromagnetic interference (“EMI”) at the back of the module difficult to achieve. Specifically, attaching the module to the front panel of the host device can result in a good EMI seal between the module flange and the host front panel. However, tolerance stackup in the plugging direction results in a highly variable position of the module connector with respect to the host connector from one module to another such that a conventional elastomeric EMI gasket, which has a limited compression range, positioned between the back of the module and the host connector is inadequate for providing EMI containment.
Additionally, the tolerance stackup is typically compensated for by increasing the length of contacts within the module connector and/or host connector. The increased contact length allows for greater variation in the position of the module connector with respect to the host connector. Additionally, however, the increased contact length increases EMI emissions of each lengthened contact and can result in large contact stubs that extend beyond the points of contact between contacts in the module connector and contacts in the host connector. The large stubs create inductive discontinuities that degrade high speed signal integrity and further exacerbate EMI emissions.
On the other hand, the back of the module can be secured directly to the host connector, rather than securing the module front panel directly to the host front panel, to improve the EMI seal at the interface between the back of the module and the host connector. Such an arrangement would additionally allow shorter contact lengths to be used in the module connector and host connector as tolerance stackup would not be an issue at that interface. However, the tolerance stackup would then have to be dealt with at the interface between the module front panel and the host front panel, preventing the module front panel from being directly secured to the host front panel and compromising the EMI seal at that interface.
Additionally, some MSAs specify belly-to-belly configurations where a first module is positioned on top of a host printed circuit board (“PCB”) and a second module is positioned upside down on the bottom of the host PCB directly beneath the first module. In such a configuration, the two modules are usually separated by only a few millimeters, or little more than the thickness of the host PCB. The presence of the oversized module front panel in the X2, XENPAK and other pluggable modules precludes belly-to-belly configurations with these modules since the oversized module front panel prevents the modules from being positioned sufficiently close together.
Moreover, thickness tolerances for PCBs are usually plus or minus ten percent. The resulting large variations in PCB thickness from one PCB to the next make it difficult to design host systems that can absorb the variations.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced